Is there a way to preserve the track changes state after using text mode?

Example of the problem
1. Set Options > Review > Track changes always off.
2. Open document in Authoring mode.
3. Enable track changes.
4. switch to text mode and make a small change.
5. Switch back to Authoring mode

Track changes are now off in the file, even though you turned them on before going into text mode. (I don't think any of my other plug-in code is causing this, let me know if you cant reproduce the issue)

Could I implement something in a WSEditorChangeListener maybe? I trued to save and store the tracking state in editorDeactivated but by then the Author page is already gone.

I understand your use case and I consider that indeed we could improve Oxygen and retain the change tracking state when the user comes back from the Text editing mode. I will add an issue for this.
About using the API, on an opened editor you can add a page changed listener: ro.sync.exml.workspace.api.listeners.WSEditorPageChangedListener which has a editorPageAboutToBeChangedVeto callback.